Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have developed conditions for efficient cDNA cloning of nanogram amounts of purified mRNAs coding for cystathionine beta-synthase [L-serine hydro-lyase (adding homocysteine), EC 4.2.1.22] and for the cytosolic precursors of mitochondrial ornithine transcarbamylase (carbamoylphosphate:L-ornithine carbamoyltransferase, EC 2.1.3.3) and the beta subunit of propionyl-CoA carboxylase [propanoyl-CoA: carbon-dioxide ligase (ADP-forming), EC 6.4.1.3]. The three mRNAs, prepared by sequential immunoselection from the same batch of rat liver polysomes, were pooled (20 ng each), and cDNA was synthesized by using avian reverse transcriptase. The second DNA strand was prepared by "nick-translation repair" of the cDNA . mRNA hybrid with RNase H, polymerase I, and DNA ligase from Escherichia coli. The double-stranded (ds) DNA was tailed with deoxycytidine residues, annealed with Pst I-cut/dG-tailed pBR322, and used to transform E. coli. The library generated by this three-step procedure contained 5000 independent colonies. A 550-base-pair (bp) cDNA clone of the beta subunit of propionyl-CoA carboxylase was detected by hybrid-selected translation; it was then used to screen the library for longer cDNAs. Two hybridizing cDNAs, 1200 and 1000 bp long with a 200-bp overlap, representing together a full-length copy of the coding region and 446 bp of 3' untranslated sequence, were recovered. Each plasmid mapped to the region q13.3----q22 of human chromosome 3. Cystathionine beta-synthase clones were obtained by screening the library with a single-stranded [32P]cDNA prepared directly from the highly purified synthase mRNA by reverse transcriptase. The longest hybridizing cDNA of 1700 bp was used in hybrid-selected translation and detected a polypeptide of 63 kDa, identical in size to rat liver synthase. In situ hybridization of this cDNA to q22 of human chromosome 21 confirmed two previous tentative assignments of the synthase locus to this chromosome.
...
PMID:Cloning and screening with nanogram amounts of immunopurified mRNAs: cDNA cloning and chromosomal mapping of cystathionine beta-synthase and the beta subunit of propionyl-CoA carboxylase. 345 73

The molecular basis of how rodent nongenotoxic hepatocarcinogens such as phenobarbitone cause liver-tumor formation is poorly understood. An early effect of phenobarbitone exposure is to induce hepatocyte proliferation transiently, and there is evidence that this may be important for subsequent tumor development. In this investigation, we have used the differential display reverse transcriptase polymerase chain reaction technique to analyze differential gene expression in male C57B1/10J mouse liver during the mitogenic phase of the phenobarbitone response. Seventy-seven putative differentially expressed cDNAs were isolated by differential display, and 13 of them were subsequently confirmed as being differentially expressed (both increased and decreased by phenobarbitone). Seven of the cDNAs were homologous to known mouse or human genes (carboxylesterase, coagulation factor X, amine N-sulphotransferase, human protein disulphide isomerase-related protein, cytochrome c oxidase subunit IV, golgin-245, thioredoxin reductase, betaine-homocysteine methyl transferase) and the remainder were novel. The expression pattern of the sulphotransferase was further characterized, and in mouse liver it was found to be significantly induced by phenobarbitone and not by five other rodent nongenotoxic hepatocarcinogens. In summary, the technique has enabled the identification of previously uncharacterized genes whose expression patterns are differentially altered by phenobarbitone in the mouse liver.
...
PMID:Identification of phenobarbitone-modulated genes in mouse liver by differential display. 1063 Apr 19

This study investigates fasting serum levels of methionine and related metabolites, vitamin B6, and folate during highly active antiretroviral therapy in therapy-naive human immunodeficiency virus (HIV)-1-infected outpatients. The research design consisted of before and during therapy measurements with a median treatment period of 100 days (range, 50 to 188) in frozen samples. The subjects included 17 consecutive HIV-1-infected outpatients (15 men and 2 women; 25 to 65-years-old). Controls were 42 healthy individuals (28 men and 14 women; 24- to 82-years-old) without serologic evidence of HIV and/or hepatitis C infection and normal clinical chemistry. Subjects received treatment with the reverse transcriptase inhibitors, azidothymidine (AZT) or stavudine (D4T) plus lamivudine (3TC) and either the protease inhibitors, indinavir (IND), nelfinavir (NELF), ritonavir (RITV), or saquinavir (SAQ) at the standard dosage. Serum concentrations of methionine, total homocysteine (tHcy), cystathionine (CYSTA), N,N-dimethylglycine (DMG), N-methylglycine (MG), methylmalonic acid (MMA), and total cysteine, as well as vitamin B6, folate, and soluble tumor necrosis factor receptor p75 were taken at baseline and during highly active antiretroviral therapy. Baseline, serum tHcy, MMA, CYSTA, vitamin B6 concentrations were not significantly different from healthy controls. There was, however, a trend towards lower folate serum concentrations at baseline in HIV-infected patients as compared with healthy controls (P =.06). There were no significant correlations between tHcy and vitamin B6, folate, or MMA. Elevated baseline levels of DMG and MG decreased significantly during antiretroviral therapy (P =.0019 and.04, respectively), whereas no significant changes in serum concentrations of CYSTA, MMA, or methionine were detected. tHcy increased in 12 of 17 patients (P =.09). HIV-infected patients displayed significant alterations (elevated DMG and MG serum concentrations) in metabolite levels of the betaine pathway in methionine metabolism, which might be positively influenced by newly initiated antiretroviral combination therapy.
...
PMID:Decrease of elevated N,N-dimethylglycine and N-methylglycine in human immunodeficiency virus infection during short-term highly active antiretroviral therapy. 1169 44

The role of L- and D-isomers of homocysteine (Hcy) in vascular versus endocardial endothelial (EE) remodeling and function is not well understood. The hypothesis is that Hcy decreases EE cell density by activating matrix metalloproteinase (MMP) and by inducing left ventricular hypertrophy (LVH) in homocysteinemic hypertensive rats (HHR). And L- and D-isomers of Hcy have differential effects in vessel and myocardium. We used: 1) spontaneously hypertensive rats (SHR) in which endogenous total homocyst(e)ine (tHcy) levels are moderately high (18 micromol/L); 2) control age- and sex-matched normotensive Wistar rats (NWR) in which tHcy levels are normal (4 micromol/L); to create hyperhomocyst(e)inemia, 32 mg/day Hcy was administered for 12 weeks in 3) SHR (SHR-H), and in 4) NWR (NWR-H) rats; 5) endogenous tHcy levels were reduced (from 18 to 12 micromol/L) in SHR by folic acid administration (SHR-F). Plasma tHcy levels were measured by HPLC and spectrophometric methods. The MMP activity, measured by zymography, is increased by chronic Hcy administration, and folic acid treatment decreases MMP activity. The collagen and transforming growth factor-beta1 (TGF-beta1), measured by reverse transcriptase-polymerase chain reaction, are increased by Hcy. Folic acid treatment decreases collagen expression and increases TGF-beta1. In vivo LV function was measured in anesthetized rats by a catheter in the left ventricle. The partial decrease in tHcy levels and no change in arterial pressure in SHR after folic acid administration, suggested that folic acid decreases one of the L- or D-isomer of Hcy, which is not responsible for an increase in arterial pressure, but may be responsible for myocardial dysfunction. The chronic Hcy administration decreases EE function in NWR and SHR. The treatment of folic acid in SHR improves LVH and EE function. Folic acid improves cardiac remodeling and EE function by decreasing one of the D- or L-isomer of Hcy and by decreasing MMP activity in HHR. These results may suggest a differential role of L- and D-isomers in vascular versus cardiac remodeling.
...
PMID:Reversal of endocardial endothelial dysfunction by folic acid in homocysteinemic hypertensive rats. 1186 51

Cystathionine-beta-synthase (CBS) catalyzes the condensation of serine and homocysteine to form cystathionine, an intermediate step in the synthesis of cysteine. We previously described essential transactivating roles for specificity protein 1 (Sp1), Sp3, nuclear factor Y (NF-Y), and USF-1 in the regulation of the CBS-1b promoter. Differential binding of Sp1/Sp3 to the CBS-1b promoter due to differences in Sp1/Sp3 phosphorylation, and Sp1/Sp3 synergism with NF-Y might, in part, explain cell-specific patterns of CBS expression. In this report, the roles of various NF-YA isoforms in influencing cell-specific differences in CBS gene expression were determined in HT1080 and HepG2 cells. Seven unique NF-YA isoforms were detected in HT1080 by reverse transcriptase-PCR (RT-PCR) and DNA sequencing, characterized by deletions in the glutamine-rich and/or serine/threonine-rich domains. Only four of the seven NF-YA isoforms were found in HepG2 cells. The six alternatively spliced NF-YA isoforms all showed significantly less synergistic transactivation of the CBS-1b promoter with Sp1 than wild-type NF-YA, as determined by cotransfections in Drosophila SL2 cells with NF-YB and NF-YC. Further, all six alternatively spliced NF-YA isoforms inhibited the synergistic transactivation of the CBS-1b promoter by wild-type NF-Y and Sp1. Thus, the cellular distributions of these alternatively spliced NF-YA isoforms could impart an important cell-specific component to CBS transcriptional regulation, by virtue of their abilities to directly synergize with Sp1/Sp3 and interfere with transactivation of the CBS-1b promoter by wild-type NF-Y. Characterization of CBS promoter structure and function should clarify the molecular bases for variations in CBS gene expression in genetic diseases and the relationship between CBS and Down's syndrome (DS).
...
PMID:Synergistic regulation of human cystathionine-beta-synthase-1b promoter by transcription factors NF-YA isoforms and Sp1. 1242 42

Oxidative stress plays an important role in the cardiovascular complications in end-stage renal disease (ESRD) patients on long-term hemodialysis (HD). Heme oxygenase-1 (HO-1) inhibits inflammatory events and protects against oxidative stress and endothelial injury. Therefore, we followed the effects of single HD sessions on HO-1 expression. A competitive reverse transcriptase PCR method was used to estimate HO-1 induction before and immediately after HD and 48 h later in 17 young uremic patients. We also measured the concentrations of plasma hemoglobin and bilirubin as indicators of hemolysis, the ferroxidase activity, and the erythrocyte-derived reduced and oxidized glutathione levels as oxidative stress markers, and the homocysteine levels as an independent risk factor. We found significant differences in HO-1 expression patterns in the patients, depending on the duration of HD treatment. Short-term HD [ n=7, median 19 months (9, 29 quartiles)] resulted in an elevated HO-1 expression, which was not further upregulated during HD. Long-term HD [ n=10, median 97 months (53, 150 quartiles)] led to downregulation of baseline HO-1 expression in ESRD patients. In these patients, a single HD session results in erythrocyte injury and a transient one- to five-fold elevation of HO-1 expression. The chronic downregulation of the baseline expression of HO-1 in long-term HD patients resulted in recurring oxidative stress during each HD session, which may contribute to accelerate the progression of atherosclerosis.
...
PMID:Heme oxygenase 1 expression in young uremic patients on hemodialysis. 1498 81

Elevated plasma homocysteine accelerates myointimal hyperplasia and luminal narrowing after carotid endarterectomy. N-methyl D aspartate receptors (NMDAr) in rat cerebrovascular cells are involved in homocysteine uptake and receptor-mediated stimulation. In the vasculature, NMDAr subunits (NR1, 2A-2D) have been identified by sequence homology in rat aortic endothelial cells. Exposure of these cells to homocysteine increased expression of receptor subunits, an effect that was attenuated by dizocilpine (MK801), a noncompetitive NMDA inhibitor. The objective of this study was to investigate the existence of an NMDAr in rat vascular smooth muscle (A7r5) cells, and also the effect of homocysteine on vascular dysregulation as mediated by this receptor. Subunits of the NMDAr (NR1, 2A-2D) were detected in the A7r5 cells by using the reverse transcriptase polymerase chain reaction and Western blotting. Homocysteine induced an increase in A7r5 cell proliferation, which was blocked by MK801. Homocysteine, in a dose and time dependent manner, increased expression of matrix metallinoproteinase-9 and interleukin-1beta, which have been implicated in vascular smooth muscle cell migration and/or proliferation. Homocysteine reduced the vascular elaboration of nitric oxide and increased the elaboration of the nitric oxide synthase inhibitor, asymmetric dimethylarginine. All of these homocysteine mediated effects were inhibited by MK801. NMDAr exist in vascular smooth muscle cells and appear to mediate, at least in part, homocysteine-induced dysregulation of vascular smooth muscle cell functions.
...
PMID:Homocysteine-induced vascular dysregulation is mediated by the NMDA receptor. 1623 75

The study has been designed to investigate the effect of 8-Br-cAMP, an activator of protein kinase A (PKA), in diabetes mellitus- and hyperhomocysteinemia-induced vascular endothelial dysfunction. Streptozotocin (55 mg kg-1, i.v.) and methionine (1.7% w/w, p.o., 4 weeks) were administered to rats to produce diabetes mellitus (serum glucose >200 mg dL-1) and hyperhomocysteinemia (serum homocysteine >10 microM), respectively. Vascular endothelial dysfunction was assessed using isolated aortic ring preparation, electron microscopy of thoracic aorta, and serum concentration of nitrite/nitrate. The expression of mRNA for p22phox and endothelial nitric oxide synthase (eNOS) was assessed by using reverse transcriptase-polymerase chain reaction (TBARS) (RT-PCR). Serum thiobarbituric acid-reactive substances (TBARS) concentration and aortic superoxide anion concentration were estimated to assess oxidative stress. 8-Br-cAMP (5 mg kg-1, i.p.) or atorvastatin (30 mg kg-1, p.o.) prevented diabetes mellitus- and hyperhomocysteinemia-induced attenuation of acetylcholine-induced endothelium-dependent relaxation, impairment of vascular endothelial lining, decrease in expression of mRNA for eNOS, serum nitrite/nitrate concentration, and increase in expression of mRNA for p22phox, superoxide anion, and serum TBARS. The ameliorative effect of 8-Br-cAMP was prevented by N omega-nitro-L-arginine methyl ester (L-NAME) (25 mg kg-1, i.p.) and glibenclamide (5 mg kg-1, i.p.). Therefore, it may be concluded that 8-Br-cAMP-induced activation of PKA may improve vascular endothelial dysfunction.
...
PMID:Activation of protein kinase A improves vascular endothelial dysfunction. 1699 Jan 83

Senescence is a mechanism that limits cellular lifespan and constitutes a barrier against cellular immortalization. To identify new senescence regulatory genes that might play a role in tumorigenesis, we have designed and performed a large-scale antisense-based genetic screen in primary mouse embryo fibroblasts (MEFs). Out of this screen, we have identified five different genes through which loss of function partially bypasses senescence. These genes belong to very different biochemical families: csn2 (component of the Cop9 signalosome), aldose reductase (a metabolic enzyme) and brf1 (subunit of the RNA polymerase II complex), S-adenosyl homocysteine hydrolase and Bub1. Inactivation, at least partial, of these genes confers resistance to both p53- and p16INK4a-induced proliferation arrest. Furthermore, such inactivation inhibits p53 but not E2F1 transcriptional activity and impairs DNA-damage-induced transcription of p21. Since the aim of the screen was to identify new regulators of tumorigenesis, we have tested their inactivation in human tumors. We have found, either by northern blot or quantitative reverse transcriptase-PCR analysis, that the expression of three genes, Csn2, Aldose reductase and Brf1, is lost at different ratios in tumors of different origins. These genes are located at common positions of loss of heterogeneity (15q21.2, 7q35 and 14q32.33); therefore,we have measured genomic losses of these specific genes in different tumors. We have found that Csn2 and Brf1 also show genomic losses of one allele in different tumors. Our data suggest that the three genes identified in the genome-wide loss-of-function genetic screen are putative tumor suppressors located at 15q21.2; 7q35 and 14q32.33.
...
PMID:Cellular senescence bypass screen identifies new putative tumor suppressor genes. 1796 25

DNA methylation is coupled with one-carbon metabolism involving homocysteine/methionine interconversion. Correlation between plasma homocysteine levels and leukocyte global DNA methylation was reported but not always replicated. Nicotinamide N-methyltransferase (NNMT) is a determinant of plasma homocysteine levels. Findings suggest alteration of one-carbon metabolism in schizophrenia etiology; hyperhomocysteinemia was observed in schizophrenia. A recent study carried out by the authors of this paper found an association between NNMT and schizophrenia and decreased post-mortem brain NNMT mRNA levels. The present study assessed the interrelationship between brain and leukocytes global DNA methylation and plasma homocysteine levels, and between hyperhomocysteinemia and brain NNMT expression. Mice were administered homocysteine in drinking water. Percentage global genome DNA methylation was measured using the cytosine-extension method, and NNMT expression was measured using real-time quantitative reverse transcriptase PCR (qRT-PCR). Homocysteine administration resulted in a 10-fold increase in plasma homocysteine. However, there was no change in global DNA methylation in lymphocytes or in the frontal cortex. No significant intra-individual correlation was found between global DNA methylation in leukocytes and frontal cortex, suggesting that leukocyte global DNA methylation may not serve as a marker for brain global DNA methylation. No difference was found in NNMT expression in homocysteine-treated mice compared with control mice. In conclusion, relatively short-term hyperhomocysteinemia in mice does not reproduce or lead to alterations reported in one-carbon metabolism in disorders associated with lifelong elevated plasma homocysteine.
...
PMID:Hyperhomocysteinemia does not affect global DNA methylation and nicotinamide N-methyltransferase expression in mice. 2116 89


1 2 Next >>

---